This invention relates to bearings, and in particular to shaped low friction bearings having fabric bearing surfaces and metal support members, and methods and apparatus for making the same.
Bearing surfaces are made from various compositions, including thermoplastic resins such as Teflon (trademark of DuPont for polytetrafluoroethylene). The following U.S. patents teach various plastic bearing compositions:
______________________________________ Inventor U.S. Pat. No. ______________________________________ Dodson, et al. 3,455,864 Ikeda, et al. 3,779,918 Cairns 3,879,301 Neinhart, et al. 3,908,038 Ikeda, et al. 3,985,661 Cairns 3,994,814 ______________________________________
Sometimes fibers, threads, or yarns comprising a low friction material, especially Teflon, is braided, wound, wrapped, knit or woven to form the desired bearing surface. The following U.S. patents disclose bearing surfaces made from low friction fibers:
______________________________________ Inventor U.S. Pat. No. ______________________________________ White 3,037,893 White Re 24,765 Osborn, et al. 3,464,845 Cairns, et al. 3,781,205 Thomson 3,033,623 Wayson 3,711,166 ______________________________________
Bearings often have backing members, typically metallic, to provide strength, rigidity, and shape. It has been a continuing problem to form the bearing and to simply yet satisfactorily fasten the low friction surface material to the backing member. It has been suggested that low friction materials be molded, sintered, glued, sewn, or clipped onto bearing backings. It has been suggested that perforations in the bearing backing may be useful in securing the low friction material to the backing. The following U.S. patents disclose bearings having perforated backing members to which a low friction material is attached.
______________________________________ Inventor U.S. Pat. No. ______________________________________ Stott 2,459,598 Cotchett 2,622,949 Terhorst 2,989,355 Prior 3,252,346 Hentschel 3,881,791 ______________________________________
U.S. Pat. Nos. 3,268,281 (Miller), 2,380,715 (Aker), and 2,310,923 (Bean) also relate to shaped bearings.
In U.S. Pat. No. 3,033,623 (Thomson), mentioned above, a bearing is made by attaching a sheet of low friction synthetic plastic material to perforated metal backing. A cylindrical bearing is then formed by rolling the sheet into the desired shape. In U.S. Pat. No. 3,711,166 (Wayson), mentioned above, a fabricated sheet of Teflon rests on a plate that has alternating depressed and raised areas.
A disadvantage of the prior art for making low friction bearings, other than simple flat bearings, is the frequent resort to specialized and complex, manual or automated methods such as molding and sintering for bonding low friction materials to backings and for forming the bearings.
Another disadvantage of some prior art for making low friction bearings is that the resulting bearing has a seam on the bearing face. For example, Pat. Nos. 3,881,791 (Hentschel) and 3,033,623 (Thomson), mentioned above, disclose bearings cylindrical in shape which have seams. U.S. Pat. No. 3,848,306 (Morse) discloses a method for making a cylindrical bearing in which a flat layer of plastic and a layer of perforated metal are bonded together to form a single sheet, which is then bent and swagged into a cylindrical tube. The resulting bearing has a seam. Such seams cause a discontinuity in an otherwise smooth bearing surface.
The various prior art manufacturing processes could be rendered more economical if the various steps for bonding low friction material to backing members and for forming the bearing backings could be reduced.